Variability in spontaneous subcellular calcium release in guinea-pig ileum smooth muscle cells
Variability in spontaneous subcellular calcium release in guinea-pig ileum smooth muscle cells
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DOI：
10.1111/j.1469-7793.1998.707bs.x
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发表时间：
1998-03-15
影响因子：
5.5
通讯作者：
Cannell, MB
中科院分区：
文献类型：
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作者：
Gordienko, DV;Bolton, TB;Cannell, MB
1. 使用激光扫描共聚焦显微镜对加载了fluo - 3的心肌细胞进行检测，观察到约40%的细胞内[Ca²⁺]ᵢ出现自发的、局部短暂性升高（“Ca²⁺火花”）。施加Cd²⁺（200 μM）后Ca²⁺火花仍然存在，但被ryanodine（30 μM）或毒胡萝卜素（0.1 μM）消除，这表明它们源于肌浆网（SR）中ryanodine受体（RyR）的自发激活。
2. 在细胞的任何共聚焦平面内的某些位点（或“频繁放电位点”，FDSs），Ca²⁺火花出现的频率要高得多，线扫描成像显示它们在空间大小、幅度和时间进程上存在很大差异。一些自发的局部瞬变与在心脏中观察到的“Ca²⁺火花”非常相似，即持续约200毫秒，峰值荧光比值为1.75 ± 0.23（平均值±标准差，n = 33）。其他事件则更快且更小，仅持续约40毫秒，峰值标准化荧光为1.36 ± 0.09（平均值±标准差，n = 28）。
3. 还观察到传播速度范围很广（在30到260 μm s⁻¹之间）的自发Ca²⁺波。在约60%的记录（n = 33）中，可以在波起始位点检测到Ca²⁺火花。[Ca²⁺]ᵢ升高的波以非恒定速度传播，在某些情况下会终止。这些观察结果可以通过亚细胞释放位点分布的异质性以及每个释放位点对波的贡献的可变性来解释。
4. 单个分散的内脏平滑肌细胞中的自发[Ca²⁺]ᵢ瞬变具有广泛的行为谱，这可能是较小局部事件时空募集的结果，可能是通过钙诱导钙释放（CICR）机制。细胞内肌浆网和ryanodine受体分布的空间不均匀性可能解释了“频繁放电位点”的存在，这些位点引发了大多数平滑肌Ca²⁺火花，以及所观察到的Ca²⁺波传播速度的广泛差异。
1. Spontaneous, localized transient increases in [Ca2+](i) ('Ca2+ sparks') were observed in about 40% of fluo-3-loaded myocytes examined using laser scanning confocal microscopy. Ca2+ sparks persisted after application of Cd2+ (200 mu M), but were abolished by ryanodine (30 mu M) or thapsigargin (0.1 mu M), suggesting that they arise from the spontaneous activation of ryanodine receptors (RyR) in the sarcoplasmic reticulum (SR).2. Ca2+ sparks occurred much more frequently at certain sites (or 'frequent discharge sites', FDSs) within any confocal plane of the cell and line-scan imaging revealed a wide variation in their spatial size, amplitude and time course. Some spontaneous local transients were very similar to 'Ca2+ sparks' observed in heart, i.e. lasting similar to 200 ms with a peak fluorescence ratio of 1.75 +/- 0.23 (mean +/- S.D., n = 33). Other events were faster and smaller, lasting only similar to 40 ms with a peak normalized fluorescence of 1.36 +/- 0.09 (mean +/- S.D., n = 28).3. Spontaneous Ca2+ waves with a wide range of propagation velocities (between 30 and 260 mu m s(-1)) were also observed. In about 60% of records (n = 33), Ca2+ sparks could be detected at the sites of wave initiation. Wave of elevated [Ca2+](i) propagated with nonconstant velocity and in some cases terminated. These observations could be explained by heterogeneity in the distribution of subcellular release sites as well as variability in the contribution of each release site to the wave.4. Spontaneous [Ca2+](i) transients in single dispersed visceral smooth muscle cells have a wide spectrum of behaviour that is likely to be the result of spatio-temporal recruitment of smaller local events, probably via a calcium-induced calcium release (CICR) mechanism. The spatial non-uniformity of SR and RyR distribution within the cell may account for the existence of 'frequent discharge sites' firing the majority of the smooth muscle Ca2+ sparks and the wide variation in the Ca2+ wave propagation velocities observed.